Soils play a central role in the global carbon cycle and constitute a large carbon reservoir. There is urgent necessity to increase our common understanding about sources, mechanisms and processes of greenhouse gas emissions from soils, and to identify those management practices which mitigate those emissions, increasing C sequestration in soils. Greenhouse gas emissions (CO2, N2O and CH4) from natural and agricultural soils still pose a challenge for scientists. Moreover, soils have a finite capacity to sequester carbon and the knowledge of key factors and processes that promote the stability of soil carbon is crucial to adopt suitable practices which lead to long-term increments in soil carbon stocks. Despite their importance for global warming and atmospheric chemistry, the process understanding is limited which hampers our ability to estimate C reservoirs and emissions for larger scales, predict emissions for future conditions or evaluate potential reduction of greenhouse gas emissions and C stocks. Important uncertainties remain among others on the effect of heterogeneities on various scales, the balance and interaction between production and uptake in the soil profile, and/or the effect of changing conditions on greenhouse gas production and emission. In addition, soils can contribute to global warming mitigation by reducing greenhouse emissions and stabilizing carbon pools. Nonethless, the capacity of soils to sequester carbon and reduce emission is finite, and the knowledge of key factors and processes that promote the stability of soil carbon is crucial to adopt suitable practices which lead to long-term increments in soil carbon stocks. Carbon adsorption to clay and silt particles, formation of micro- and macroaggregates, humification processes, charcoal formation, carbonates precipitation, etc., can stabilize carbon for long periods. These processes are complex and no techniques are currently available to accurately describe the continuum of soil organic and inorganic matter.
The purpose of this session is to get a state of the art overview of recent findings and future research challenges about physical, chemical and biological processes controlling carbon sequestration in soils and greenhouse emissions from soils, together with the adoption of management practices more prone to favour decreased emissions and long-term soil carbon stock increments. In this session, we welcome studies on soil organic and inorganic matter dynamics, organomineral interactions and biological activities, new techniques to assess soil greenhouse emissions and organic matter quality and stability, at all scales, ranging from controlled lab experiments, field studies to model studies.